Greg intends to place a 300 square foot pool in his back yard. if the width of the pool is 5 ft shorter then the length, what are the dimensions of the pool?

We have

L (L-5) = 300 simplify

L^2 - 5L= 300

L^2 - 5L - 300 = 0 factor, if possible

(L -20) (L + 15) = 0 so .. setting the factors to 0, we have that L = 20 and L = -15

Reject the -15

So

L = 20

And the width is 5 less = 15